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SQL Fundamentals

SQL, or Structured Query Language, is the go-to language for managing relational databases. It allows users to interact with databases to retrieve, manipulate, and control data efficiently. SQL provides a standardized way to define database structures, perform data operations, and ensure data integrity. From querying data to managing access and transactions, SQL is a fundamental tool for anyone working with databases.


1. Basics of SQL

  • Introduction: SQL (Structured Query Language) is used for managing and manipulating relational databases.
  • SQL Syntax: Basic structure of SQL statements (e.g., SELECT, INSERT, UPDATE, DELETE).
  • Data Types: Different types of data that can be stored (e.g., INTEGER, VARCHAR, DATE).

2. SQL Commands

  • DDL (Data Definition Language):
    • CREATE TABLE: Define new tables.
    • ALTER TABLE: Modify existing tables.
    • DROP TABLE: Delete tables.
  • DML (Data Manipulation Language):
    • INSERT: Add new records.
    • UPDATE: Modify existing records.
    • DELETE: Remove records.
  • DQL (Data Query Language):
    • SELECT: Retrieve data from one or more tables. 
  • DCL (Data Control Language):
    • GRANT: Give user access privileges.
    • REVOKE: Remove user access privileges.
  • TCL (Transaction Control Language):
    • COMMIT: Save changes.
    • ROLLBACK: Undo changes.
    • SAVEPOINT: Set a save point within a transaction.

3. SQL Functions


4. Joins

  • INNER JOIN: Returns records with matching values in both tables.
  • LEFT OUTER JOIN: Returns all records from the left table and matched records from the right table.
  • RIGHT OUTER JOIN: Returns all records from the right table and matched records from the left table.
  • FULL OUTER JOIN: Returns records when there is a match in either left or right table.
  • CROSS JOIN: Returns Cartesian product of the two tables.
  • SELF JOIN: Joining a table with itself.

5. Subqueries


6. Indexes


7. Views


8. Constraints

  • NOT NULL: Ensures that a column cannot have a NULL value.
  • UNIQUE: Ensures all values in a column are unique.
  • PRIMARY KEY: Uniquely identifies each record in a table.
  • FOREIGN KEY: Ensures referential integrity between tables.
  • CHECK: Ensures that the values in a column satisfy a specific condition.
  • DEFAULT: Sets a default value for a column.

9. Transactions

  • ACID Properties: Atomicity, Consistency, Isolation, Durability.
  • Isolation Levels: READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, SERIALIZABLE.

10. Advanced Topics

  • Stored Procedures: Precompiled collections of SQL statements.
  • Triggers: SQL code that automatically runs in response to certain events on a particular table or view.
  • Cursors: Used to retrieve, manipulate, and navigate through a result set row by row.
  • CTE (Common Table Expressions): Temporary result set defined within the execution scope of a single SELECT, INSERT, UPDATE, or DELETE statement.
  • Window Functions: Perform calculations across a set of table rows related to the current row.

11. Performance Optimization


12. Security


This overview covers the foundational and advanced topics of SQL, providing a structured path for learning and mastering SQL.

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